Germany is returning to Italy more than 500 valuable antique books stolen from Italian libraries about three years ago. An Italian librarian has been convicted in the theft of the collection that includes such priceless texts such as the first editions of scientific manuals by Galileo and Copernicus.

Most of the books are from the 16th and 17th centuries. Their total value is estimated at close to $3 million. German authorities say that the auction house in the Bavarian city of Munich has agreed to return them to their owners at Italy's request.

"These books come from Italy, from Naples, from the Girolamini library. They are very valuable, from the 15th to the 17th century. They are scientific books, some by Galileo, by Copernicus. They are extremely valuable, and they were stolen from the library over the course of a couple of months," said Elisabeth Zumbruch, chief crime commissioner at Bavaria's National Crime Office.

Naples-based prosecutor Vincenzo Piscitelli said the director of the Baroque-era library, Massimo de Caro, had been convicted of the theft and sentenced to prison.

"He deactivated the security alarm systems, carried out his activities during night hours or during the holidays, when the library staff was not there, he was alone, he had the keys, everyone knew he was the director - therefore he was able to work in complete freedom," said Piscitelli.

He also said that the full extent of the thefts had not yet been determined.

"We don't know yet how many books in total were taken," he said. "However, since we are talking about more than 500 books that were returned, this is one of the most important recoveries in our investigations to reconstruct the compendium of the library."

Italian mathematician and astronomer Galileo Galilei and Polish Nicolaus Copernicus are among the most influential natural scientists of the early modern age, and their findings are documented in the texts that were stolen over a period of time in 2012. Bavarian police said the books would be placed in special boxes for their return to Italy.